Science & Technology

Cleansorb, a leading provider of chemical well treatments that enhance hydrocarbon production for the international oil and gas industry, announces that it is helping a major operator to enhance recovery from a maturing field offshore U.K.

As part of field redevelopment, effective drilling damage removal in new water injector wells is critical to achieving target injection rates without fracturing the reservoir. Openhole injector wells with sand screens are being treated with ORCA™ for WBM to remove water-based mud drilling damage. The operator is aiming to extend the life of this 20-year old field for an additional 20 years or more with these injection and associated production wells.

Injector wells hit target injection rates following ORCA treatment

Already, six injector wells have been treated with ORCA for WBM to thoroughly remove carbonate/polymer DIF filter cake from the reservoir wellbore face before starting water injection. Without this, residual drilling damage was predicted to prevent water injection under matrix conditions, resulting in pressure build-up and unwanted fracturing of the formation. Upon starting water injection, each of the six ORCA treated injector wells have hit their respective target injection rates at well below formation fracture pressure. In addition, this was achieved without back flowing wells prior to injection, saving this valued customer time and money.

“The ORCA for WBM mud damage removal treatments carried out on these injector wells offshore U.K. are achieving one of the precise benefits we developed the ORCA treatment line to achieve: maximizing drilling damage removal to improve injectivity in injection wells, especially where matrix injection is required,” said Ian Mckay, Director & Co-founder of Cleansorb. “As with all of our well treatment formulations, ORCA improves well productivity with minimal risk to personnel, the environment and equipment. This ongoing offshore U.K. treatment programme is a perfect example, providing further evidence that this field-proven technology performs reliably, boosting well performance, safely and cost-effectively.”

Looking ahead, two more injector wells on this particular field redevelopment are scheduled for treatment in 2018. Satisfied with the increased injectivity it has realized from the ORCA treatment programme, the operator is assessing possible use of ORCA for other future field developments.

Delivering results around the world

The proprietary chemistry of ORCA for WBM dissolves drilling fluid filter cakes and other acid soluble damage caused by water-based drilling fluids. It is used in a wide range of types of completions in oil and gas production wells, as well as water and gas injection wells. As a result, ORCA for WBM has been used to treat hundreds of wells across every major oil and gas operating region in the world.

The Cleansorb approach to optimizing injectivity

With the price of oil having remained low over the past few years, operators are shying away from constructing new wells in frontier areas, often opting to maximize output from existing producing fields.

Injection wells have a dual role to play in helping operators squeeze more production from their assets. Following years of production, injectors provide pressure support to aging reservoirs as formation pressure falls. In EOR applications, strategically located wells may be repurposed as injectors or new injector wells may be drilled. Water or engineered fluids are then injected to drive hydrocarbon deposits towards producing wells.

In both of these instances, using a well to deliver fluids to the formation – rather than extracting fluids from the formation – brings a unique set of challenges to be overcome. Fluids must be able to be injected uniformly along the target interval. Any barriers to injection can cause unwanted injection pressure build-up that risks fracturing the reservoir rock, affecting fluid placement and efficient “sweeping” of hydrocarbon from the reservoir. Drilling mud residues from the near wellbore area can also be pushed out into the formation, adversely affecting the injectivity of the well.

Given the growing importance of injection wells to future oil production, it’s clear that addressing drilling damage with an effective wellbore clean-up strategy is critical to maximizing injectivity. The key to uniform drilling damage removal lies in the comprehensive removal of this damage across the entire injection interval.

The conventional approach is to spot acids in the wellbore to break down mud filter cake. HCl acid-based treatments dissolve any carbonate component that may be present as drilling cuttings fines from the formation or added at surface as a weighting agent. However, achieving this uniformly across long intervals is problematic, if not impossible. Also, water-based reservoir drill-in fluids typically include biopolymers, such as starch, cellulose and xanthan, and many operators are finding that these polymeric components cannot be tackled effectively by acid alone.

After reviewing the specific chemical composition of a drill-in fluid and the downhole conditions where it will be used, Cleansorb technicians select an ORCA treatment fluid formulation specifically for this application. Selected ORCA formulations are tested in the lab at reservoir temperature to confirm they effectively disrupt mud cakes prepared from corresponding drill-in fluid samples.

Then, the effectiveness of proposed ORCA formulations is typically quantified by operators using regain permeability coreflood tests. These compare the permeability of reservoir rock core plugs: In their original state before treatment; After applying a drill-in fluid squeeze to the core face to simulate drilling damage and then treating this under reservoir conditions with the selected ORCA fluid formulation.

By measuring the regain permeability, operators can confirm the target permeability required to achieve target injection rates. As this validation work occurs before well treatments take place, Cleansorb’s approach increases treatment efficiency while reducing the risk of failure.